Status of LHAASO-WCDA Mingjun Chen Jul 14th , 2017 LHAASO L arge H - - PowerPoint PPT Presentation

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Status of LHAASO-WCDA Mingjun Chen Jul 14th , 2017 LHAASO L arge H - - PowerPoint PPT Presentation

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Status of LHAASO-WCDA Mingjun Chen Jul 14th , 2017 LHAASO L arge H igh A ltitude A ir S hower O bservatory LHAASO site Location: Four types of detectors: 29 2130.7N, 100 0814.7E; The Electromagnetic particle Detector

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SLIDE 1

Status of LHAASO-WCDA

Mingjun Chen Jul14th , 2017

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SLIDE 2

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LHAASO site

LHAASO

Large High Altitude Air Shower Observatory

 Location: 2921’30.7”N, 10008’14.7”E;  4,400 m a.s.l;  700 km to Chengdu;  8 km to airport;  50 km to Daocheng City.

Four types of detectors:

  • The Electromagnetic particle Detector

(ED) array --5195 units

  • Muon Detectors Array --1171 units.
  • Wide Field Cherenkov Telescope Array
  • WCDA
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SLIDE 3

WCDA - Water Cherenkov Detector Array

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3 water ponds:

  • 78,000 m2 in total;
  • 4.4 m water depth;
  • 3,120 cells, with an 8”/9” PMT in each cell;
  • Cells are partitioned with black curtains.

Detect shower secondary particles:

  • Electrons/positrons;
  • Muons;
  • Gammas.
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SLIDE 4

Physics Goals

VHE gamma sky survey (100 GeV-30 TeV):

Extragalactic sources & flares;

VHE emission from Gamma Ray Bursts;

Galactic sources;

Diffused Gamma rays.

Cosmic Ray physics (1 TeV-10 PeV):

Anisotropy of VHE cosmic rays;

Cosmic ray spectrum;

Cosmic electrons;

Hadronic interaction models.

Miscellaneous:

Gamma rays from dark matter;

Sun storm & IMF.

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SLIDE 5

Schematics of WCDA

Nine Cells Nine Cells Nine Cells Nine Cells

FEE FEE FEE FEE DAQ & Data storage

Time calibration system

Clock system 3,120 cells Slow control system Water purification & recirculation system HV system

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SLIDE 6

Engineering of Water Pond

Major pollution is TOC/DOC: UV185 + 0.22 m. Water flow: 1 volume/month

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SLIDE 7

Photo Multiplier Tube

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Large area Single Photonelectron Large dynamic range High time performance Low noise rate 8-in/9-in P/V>2.0 Anode & Dynode outputs TTS<4.0ns Noise rate<5KHz Candidates：

  • R5912
  • CR365
  • XP1805

HZC XP1805 Work gain:3*106 Average Amplitude of SPE: ~5mV Polarity of HV: Positive Three 30m cables: Two signals + One HV FEE HV

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SLIDE 8

Readout Electronics

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PMT

Charge Measurement Time Measurement Buffer Data Readout Buffer Anode Dynode 8

FPGA

Charge Measurement

  • 9 PMTs share a FEE board.
  • Charge/ADC: filter & shaping with RC2，peak finding with FPGA;
  • Time/TDC: leading edge discriminating, time being measured with FPGA-TDC (bin-size 0.333 ns);
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SLIDE 9

DAQ & Data

Online Computer Room

Online Farm （Blade servers） Storage Server × 2 File&Manager server × 2 Switches

Control Room

Disk Array Fiber Twisted-pair DAQ PC × 2

Web server

To Internet

A computer cluster consists of ~4,000 CPU cores;

Software implementation is based

  • n the ATLAS TDAQ framework.
  • Data are transferred to a computing

center at IHEP (or other site) via commercial network links;

  • Data are stored (disk + tape), accessed

and processed in the infrastructure of the computer center.

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SLIDE 10

Slow Control system

Monitor environment parameters(temperature, pressure, humidity, water depth, …);

Monitor & control of HV of PMTs;

Water attenuation length measurement.

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SLIDE 11

Time Calibration

 Cluster-based, cross-calibrated:

 2 fibers per PMT seperatively;  2 LEDs per cluster, lit in turn;  2-4 fibers are crossed over

neighboring clusters;

 Frequency of LED pulsing: 5-10 Hz.

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SLIDE 12

Charge Calibration

Low range: single rate (peak-i)

~20 kHz;

SPE signal dominated;

Including PMT Gain + cable + pre-amp + low range electronics.

 High range: muon peak

(peak-iii)

 ~10 Hz;  Vertical muons hitting the

photo-cathode;

 PMT high range gain + QE +

CE + cable + pre-amp + high range electronics.

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SLIDE 13

Sensitivity

积分灵敏度

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0.013crab@2TeV

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WCDA Specifications

Item Value Cell area 25 m2 Effective water depth 4 m Water transparency > 15 m (400 nm) Precision of time measurement 0.5 ns Dynamic range 1-4,000 PEs Time resolution <2 ns Charge resolution 50% @ 1 PE 5% @ 4000 PEs Accuracy of charge calibration <2% Accuracy of time calibration <0.2 ns Total area 78,000 m2 Total cells 3,120

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R&D work(I): a prototype unit

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Diameter:7m Height: 5m

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R&D work(II): Nine cells engineering array at Yabajing

The space angles of the reconstructed shower directions between the two experiments for the matched shower events. 16

A reconstructed shower-core distribution from ARGO-YBJ for the GPStime-matched events of the prototype array and ARGO-YBJ.

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SLIDE 17

Collaborators & Schedule

University of Science and Technology of China

Electronics, PMTs

National Space Science Center, CAS

Slow control system

Tsinghua University

WR Clock system

Institute of High Energy Physics, CAS

Detector installation, DAQ, data, etc.

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SLIDE 18

Collaborators & Schedule

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2018.6 Start detector installation of the 1st pond. End of 2018 Installation finished of the 1st pond. Beginning of 2021 Completed.

University of Science and Technology of China Electronics, PMTs National Space Science Center, CAS Slow control system Tsinghua University WR Clock system Institute of High Energy Physics, CAS Detector installation, DAQ, data, etc.

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SLIDE 19

Summary

 LHAASO-WCDA, as a component of LHAASO

project, aims at playing an important role in the Gamma astronomy.

 WCDA already started construction. And one

quarter of array will start operation in the end

  • f 2018.

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SLIDE 20

Thank you all.

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SLIDE 21

Backup

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VHE -astronomy: Two Techniques

IACTs: H.E.S.S., VERITAS, MAGIC, …

Good angular resolution (~0.1);

Fair background rejection power;

Short duty cycle (~10%);

Narrow FOV (<5);

Low energy threshold (~100 GeV);

 Mainly focused on deep observation. 22

 Ground particle array: AS, ARGO-YBJ, Milagro, HAWC, …

 Not-so-good angular resolution (~0.5);  Poor background rejection power (but much elaborated in water Cherenkov);  Full duty cycle (>95%，~10 IACT);  Wide FOV（>2/3，~150 IACT);  High energy threshold  improved by construction at high altitude (~1 TeV);

 Good at sky survey, extended sources and flares.

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SLIDE 23

Unknown TeV Sources

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 Kifune’s plot: new detectors on TeV Gamma rays are

awaited to keep the discovery pace. The LHAASO detectors will do help.

 Can the number of sources climb to ~1000 by 2020?

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SLIDE 24

 依赖于簇射芯位距阵列中心的距离（R）：

nPMT20：>60%的事例能够触发；

nPMT30：>90%的事例能够触发。

WCDA project--触发模式

以12*12个单元为一组；

相邻组由一半重叠；

各个通道的阈值设置1/3PE

组内250ns有多个PMT着火时 触发, 比如12个，就只有小于 1KHz的噪声触发。

Noise trigger

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SLIDE 25

Gamma/proton Discrimination

Proton Gamma

 Brightest “sub-core”:

 Signal of the brightest PMT outside the

shower core region (e.g., 45 m);

 “Compactness” can be employed to

reject cosmic ray background efficiently.

 Q-factor: 7 @ 1 TeV; 22 @ 5 TeV.

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SLIDE 26

Effective Area & Angular Resolution

 Effective area:

 ~1,000 m2 @ 100 GeV; >80,000 m2 @ 5 TeV.

 Angular resolution:

 Optimized bin size: 0.55 @ 1 TeV; 0.23 @ 5 TeV.

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